Re: [ST] Tires for a 2000 RS

>From: Dan Wetherington
>I'm curious as to their complaints about the Avons, as well as their
>test methods. Could you provide some more details?
Here's the whole test, in Dutch though:
http://www.motorbike.demon.nl/griporslip.pdf
Almost the whole article is giving background on how and why they tested,
but I'll try to summarize and translate for you. Originally the huge German
Motorrad mag did this test, Motoplus is the Dutch related version of the mag.
The tests was done with two R6's (one as a backup in case of crashing),
done on the Spanish circuit of Calafat, where they tested over the course
of several days for about 6 hours per day. Only 6 hours, because they
wanted as little difference of temperature (for both asphalt and air) as
possible, between first and last day. Their maximum limit was 8 degrees
Celcius of difference. A track was chosen because of the constant conditions
a track can supply. Tire temps on a track can get pretty warm though, and
a tire being too warm is not a good thing (it goes from sticky to slippery).
Before the track testing they measured relevant tire temps on twisty normal
B roads so that they would have correct reference temperatures once riding
on the track. Translated that means they had testriders complete 5 rounds
at high pace, comparable with the pace on twisty B roads. When doing that
the tires wouldn't go higher thatn 50 degrees C (riding track normally can
increase tire temps to 70 to 80 degrees C, not a normal range for sport
touring tires). Only after completing these 5 laps the limits of the tires
would be explored by searching for max bank angles and by accelerating
rapidly until reaching the loss of grip.
The results of testing these tires was amazing, since the maximum corner
was only, on average, 4 km/h lower than real sport tires. They were also
able to reach extreme lean angles of 50 degrees. So hardly any difference
there, the main difference with sport tires is that sport touring tires
will suffer when reaching the high temps you get when riding on a track
and the kind of behaviour when, at such extreme lean angles, you'd open
the throttle fully. With sport touring tires you need to throttle up
slowly and that's where the difference in lap times come from, not from
pure cornering speed.
For measuring they used a datalog system with GPS sensors. From the parameters
turn radius, cornering speed, tire width and center of mass, they were able
to compute the lean angle to 1 degree accurately. Tire temp was also measured
frequently.
The wet track tests were done on the tire test circuit of Kleber in the south
of France. The R6 at that time made one little crash, but nothing big.
Test criteria (see table in page 5):
- Handling: this was measured by the amount of countersteering needed to
bank the bike, to keep it banked and to keep it on the desired track in
a turn.
- Steering precision: Here it is measured whether the bike will stay
on the desired track through a turn or that it needs correction, while
holding a fixed amount of countersteering input, measured in fast turns.
- Grip in turns: riding on the limit of the tires in turns to see how
the sides of the tires can guide the bike, dry and wet.
- Grip in turns during acceleration: Same as above, while adding power.
- Cornering stability: how stable is the ride during fast turns, turn
combinations and unequal / bumpy road conditions.
-Behaviour on the limit: controlability of the tire on the grip limit,
on dry and wet track.
- Stand-up behaviour: during braking the bike, depending on the amount
of force, the bike will go more or less upright.
- Tire pressure 2.3 bar front, 2.5 bar on the rear on all tires.
Wet road testing:
On the special wet test track of Salon de Provence there are two
extremely slippery surfaces at passage 5 and 6, simulating the
level of grip you will find on worn mountain pass roads in the
Alps. The rest of the track is high grip asphalt. Since the cornering
speeds (especially measurable on the limits on longer turns) were
measured with GPS and not wheel turns, there was no influence of tire
slip or smaller wheel diameters. That enabled precise measuring of
cornering speed difference.
"Complaints" about the Avons Azaro:
- Cornering behaviour: The English Azaro, with their chunky profile, is
suffering from a carcas of the rear tire which is too soft, causing it to
sag down in turns that are driven hard. That causes a decrease in stability
and grip. Behaviour when turning into corners and steering precision are
very acceptable though and the stand-up behaviour is within limits.
- Test wet track: Especially on slippery, wet asphalt the Avon has
insufficient traction and tire-edge stability. That, while on the rougher
surface, it shows satisfactory riding behaviour. Obvious and partly abrupt
slides of the frontwheel don't contribute well to a subjective safety feeling.
- Avon Azaro conclusion: The normally cheaply priced Avon tires don't show
and safety related shortcomings, but because cornering stability falls short
and because it barely has sufficient safety buffers, the Azaro looses the
connection with the competition.
Enough details for you?
Emile
www.piloot.com
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